Not really Indian Summer yet, but filter with Nik's Color Efex Pro Complete's "Indian Summer" setting. I had had my eye on Color Efex Pro for along time but the price was too high. It was recently reduced enough for me to buy it. I still enjoy Silver Efex Pro more. Have to learn to effectively "tweak" the settings in Color Efex to get results that make me say "Wow". I think this one was pretty effective. Here's a nice tutorial: http://www.digital-photography-school.com/enhancing-your-images-with-nik-color-efex-pro